Speed Can Matter In Ultras, Part Four

[Author’s Note: This is part four of the series ‘Speed Can Matter in Ultras’ focusing on the presence of shorter-distance speed potential in ultramarathoning. In part one, we interviewed Emily Harrison after her impressive run at the 2014 USATF 50k Road National Championship. Part two was a discussion withRob Krar, Matt Flaherty, and Zach Bitter. Part three hosted a similar discussion with Meghan Arbogast, Caitlin Smith, and Emily Harrison. In this part, we hear from Tyler Sigl, Megan Roche, Tim Tollefson, and Beverley Anderson-Abbs, who have all run impressively fast races in 2014.]

Tyler Sigl, 28, has quietly dominated the 50-mile distance over the last two years. UltraRunning Magazine deemed his 5:38:49 course-record win at the 2013 The North Face Endurance Challenge (TNFEC)–Wisconsin50 Mile a Top 15 Age Graded Performance last year. The former University of Wisconsin–Platteville runner and 2012 U.S. Olympic Marathon Trials qualifier improved his time on the course this year, winning the 2014 TNFEC–Wisconsin 50 Mile in a staggering 5:27:55—a full 27-plus minutes faster than anyone has ever run the course before, which includes the likes of former course-record holders Zach Bitter, Matt Flaherty, and Ian Sharman.

Twenty-four-year-old Megan Roche (formerly Deakins) is no stranger to domination either: the Duke University graduate and California resident has 11 races to her name(s) on UltraSignup and—you may not believe this—she has won every single one. That includes her first ultra-distance race—the 2014 USATF 50k Trail National Championship at the Flagline Trail Fest 50k in Bend, Oregon last month—where she bested a competitive field and flew to a new course-record time of 4:00:40.

On the topic of flying, 29-year-old Tim Tollefson can do just that. The 2:18 marathoner based in Mammoth Lakes, California crushed his first ultra attempt in winning the men’s side of the 2014 USATF 50k Trail National Championship in, you guessed it, another course-record time of 3:24:05 against a national-class field.

If you thought that youth was the underlying factor for blazing-fast finish times, think again. Fifty-year-old Beverley Anderson-Abbs, over a decade removed from her first ultra, continues to get faster—contrary to the idea that speed and age are inversely related. In February, the former adventure racer and California resident (and Canadian citizen) broke her own Canadian national record and set a new personal-best time at the Jed Smith 50Mile in running a stout 6:14:46 and breaking the previous course record held by Meghan Arbogast.

Astoundingly, each of the aforementioned wins in 2014 by Sigl, Roche, Tollefson, and Anderson-Abbs included staunch new course records. What accounts for these remarkable performances? The keys that led to the speedy successes of these four runners in 2014, as can be seen below, include consistency in training, incorporation of speedwork, and a real focus on in-race nutrition. In the following interviews, Sigl, Roche, Tollefson, and Anderson-Abbs disclose details about training, race strategy, ultra-fast workouts, and future goals.

Interview with Tyler Sigl

iRunFar: Your 5:38:49 at TNFEC–Wisconsin 50 Mile was nearly 20 minutes faster than the previous course record and 17 minutes faster than second-place finisher Brian Condon. What was your preparation like for that race—did it differ from road marathon training?

Tyler Sigl: Last year I didn’t change training at all for [TNFEC–Wisconsin 50 Mile]. I was focusing on the U.S. Marathon Championships that year, which was at Twin Cities, and that was four weeks after The North Face race. So I just did my normal training for that [marathon], and figured my long runs for the marathon—24 or 25 miles—would be enough to carry me through the 50 miles. It was essentially just my weekly long run, tempo Tuesday, fartleks on Thursday, throw some hill repeats in there every once in a while, and then some easy days.

iRunFar: What kind of distances and times were you running on the tempos and fartleks?

Sigl: It would depend on how quick a tempo I did but it would usually be between five- and 10-mile tempos. At five miles it would be 4:55 or 5:00 per mile pace and for 10 miles it would be like 5:10, 5:15 per-mile pace. I was getting some trail miles in on some singletrack mountain-bike trails, so had some good hill training there. I prefer running on the trails as much as I can but it’s hard to find a lot of them in [the Green Bay area]. Overall mileage last year was pretty much 85 per week. On fartleks, I do power-pulls. It’s probably two-and-a-half to three minutes on and 15 to 20 seconds off. It depends how many pulls in a row I do, in terms of pace, but it’s usually about an hour run and it’s always sub-five-minute pace per mile.

Tyler Sigl on his way to winning the 2014 TNFEC Wisconsin 50 Mile. Photo: Jessica Sigl

iRunFar: This year, you ran a jaw-dropping 5:27:55 on the same course. What did the year between these races look like, in terms of training?

Sigl: My winter training had a big change after having my daughter. I’d get done with work, pick her up at 3:30 p.m., and my wife wouldn’t get back until 7 p.m. So trying to get any kind of training in was pretty difficult. From November through March I’d pick my daughter up from daycare, bring her home, put her in her play area in our living room next to the treadmill, and I’d run on the treadmill for as long as she’d stay content playing with her toys and enjoying some snacks. Once she’d start to make a fuss I’d be done for the day. It would be between five and seven miles of crazy-fast workouts. Essentially just tempos and any kind of speed I could get in on the treadmill. Gotta’ love Wisconsin winters.

And then this past summer I switched out a fartlek day and did more of a longer run that day and my weekly long run I upped from 25 or so miles to 30 to 31 miles. I did those at 5:50 to 6:00 pace per mile, the long runs. Still had tempo Tuesdays, which I like to do. Those were between 10 and 15 miles this time, not quite as quick, usually around 5:15, 5:20 pace per mile, as long as I could go. My mileage stayed right around 85, so I either eased off more on my easy days or took a day off.

iRunFar: So week in, week out, you were doing a 30 miler every weekend?

Sigl: Yep, I did that for about three months or so, four months. All of those were on the roads by my house. It’s flat out here, there are some hills, but I have to really search them out. There are little rollers but I don’t consider them hills. My goal has been to lower my ‘cruise pace’ to around six minutes per mile or under. It takes time, but I finally got there.

iRunFar: Do you think your shorter-speed background, running the 8k and 10k in college and after, and racing the marathon on the road for some time, sets you apart and gives you an advantage in ultras?

Sigl: Yeah, the speed training I think is a huge, beneficial background. It helps teach you to push through a lot of the pain when it gets tough and running through when you’re tired. Even with just a 20 x 200-meter workout, you get tired after 10 and you have to teach your body to push through the rest of the intervals. And when you run so many miles at faster paces, your cruise speed becomes quicker.

iRunFar: How did the experience of your first ultra last year help you this year?

Sigl: Well, last year, I had half a bottle of fluid and a couple energy blocks left when I got to an aid station and I thought I would be fine so I ran right through it. About two miles later I ran out of fluid and by the time I got to the next aid station I was like, Oh my, please don’t bonk, please don’t bonk! This year I made sure I had a full fluid bottle after each aid station and enough gels and blocks and stuff. As soon as you start running out of gas it gets pretty difficult out there. And I practiced nutrition in training. When it was hotter out in training I would do a 10-mile loop and made sure I had fluid available.

iRunFar:You just won the Fall 50 Mile last weekend, which served as the 2014 USATF 50-Mile Road National Championship. Walk us through your race.

Sigl: Going into the race I didn’t really know what to expect. Since TNFEC–Wisconsin, my mileage was limited due to an ankle sprain and some tendinitis in my right knee and ankle. I didn’t know what my race plan was going to be until the gun went off. At that time, I said, “Today I’m going to try to break five hours.”

I ran the first couple of miles with Zach Bitter and a couple of other guys (6:31, 5:51, 6:07). After about three miles, the pace felt a little too comfortable so I picked it up a little bit and ran solo from there on out. Mile after mile, I started to put a little time in the bank and continued to feel good… until mile 24.

At the 24-mile mark, the tendinitis started to flare up. By mile 32 my banked time had dwindled away and I was back to six-minute average pace for the race. At this point in the race, I felt like I couldn’t continue on due to the pain, but I pushed on. I told myself, As long as I’m in the top five, I’m staying in this race even if I have to crawl. Mile after dreaded mile I managed to run/walk/hobble to maintain first place all the way to the finish (5:32:24 – 6:39 minute-mile pace).

It wasn’t my fastest 50-mile race but it sure hurt the most. It was a beautiful course, very well organized and a fantastic after party. I can’t wait to defend my title on the same course next year, I just hope it doesn’t hurt as much.

The 9:19 at mile 40 had a big hill that I walked up the whole thing. It took four minutes to walk up. No shame in walking.

iRunFar:What are your goals going forward?

Sigl: I don’t have too much interest in going beyond 50 miles at this time. 100k I could see in the near future, but 100 miles, I don’t know, we’ll have to see. I think I’ll focus on shorter distance, 5k, 10k, half marathon, and a few 50 milers next year.

Interview with Megan Roche

iRunFar: You have won all 11 trail races listed to your names—Megan Deakins (formerly) and now Megan Roche—on UltraSignup! Have you ever lost?

Megan Roche: That’s funny; I’ve never actually searched UltraSignup so I was not aware of that. In terms of trail races, I have had my butt kicked in NCAA. [Writer’s Note: She ran one year of cross country and track at Duke University after playing field hockey the first four years there.] I came in fourth at the [2014] U.S. Mountain Running Championship and 21st at the [2014] World Mountain Running Championship. I feel like I’m more of a speed runner—going up isn’t necessarily my passion but I did enjoy that.

iRunFar: What motivated you to run an ultra?

Roche: Actually it was interesting. I raced over in Italy the week before Flagline. To be honest, I very rarely do any sort of taper but I had tapered for Italy. So I was over in Italy and after the race, I’m jet lagged, tired, had a bunch of schoolwork to catch up on. I wound up taking an easy week also after Italy. I was looking at races, I had this huge taper, I thought, I might as well use it. So Flagline was kind of the perfect opportunity. It could have been a half marathon and I would have done it; it was more about the timing of the race and less about the fact that it was an ultra.

iRunFar: Had you ever thought, One day I’m going to run an ultra?

Roche: It had occurred to me. I have known for a while that I like endurance events—I’ve done a lot of century bike rides and events that are a little bit longer, although I had never really run more than 20 miles. I had known I wanted to get into endurance but it happened a little bit sooner. My philosophy has been to really work on speed while I’m young and while I still have that ability [to run fast]. So it was sooner than I thought.

iRunFar: What was the most difficult part of your first 50k?

Roche: What surprised me, actually, was that I was planning to be conservative but as soon as I hit the starting line I just went. When I hit the starting line of races, I have no self control and I just hammer. What surprised me was that I didn’t panic. I hit 15 miles way faster than I probably should have but I just went with it and it turned out okay. I felt a lot better than I was expecting at the end. One of my strengths is being able to eat a lot while I run. I consumed, I think, 12 gels during the race, which is a little bit ridiculous. Between the caffeine and the sugar I was just ready to go.

iRunFar: You won the 2014 USATF 50k Trail National Championship at the Flagline 50k, your first ultra, by 10 minutes and set a course record. Did you feel prepared to run that fast or did you surprise yourself?

Roche: It’s funny. I don’t train for ultras. My longest run in the last six months leading up to the race was 15 miles. But I do a lot of long climbs on training runs and I think, whenever you can do a long climb and then recover on the downhills, it is like stringing two training runs into one. And being naïve helped me, too. I went out faster than planned but didn’t panic. I was mostly focused on training for Italy, which was an 8k climb. The climbs at Flagline were nice and graded so it was quite welcome.

iRunFar: What did your training look like ahead of Flagline and what sort of speed workouts did you run? Do you ever run with your husband, who finished fourth at Flagline, David Roche?

Roche: I really do a lot of speedwork. My goal is to train like an athlete. When you are on trails, athleticism comes out a lot more. A lot of my training is focused on harnessing my athleticism. That’s why I do a lot of speed workouts, I think they are a lot of fun, not because they are necessarily better for training. My go-to workout is probably a 20-minute tempo and then strides and then 10 by 60-second hills. That’s one of my favorites; I do that probably once a week. I also like doing 15 by 200 meters on the track. And then I just extend my long hill climbs to longer distances. When I do those fast workouts, I roll through the recovery, I don’t take a lot of recovery and so the overall pace usually turns into a tempo pace. The average pace in the end will be under six minutes per mile including the recovery. I also like doing wind sprints. I go to a soccer field sometimes and do diagonals. Sometimes I’ll just go out and run 12 miles hard. And I always have a rest day. David and I run all the time together actually. We just ran 20 miles together this morning.

iRunFar: In what ways, if any, do you think your shorter-distance racing background helps you at ultra distances—does it set you apart?

Roche: Yeah, I think the nature of trail running is that you are using both slow-twitch and fast-twitch muscle fibers as you are dodging over rocks and going through switchbacks. So I think having that ability to use those fast-twitch muscle fibers, it gives you an advantage, to be able to use both those systems during the race. And for me the pace on the trail seems much more comfortable because you end up going a lot slower [than in speed workouts].

iRunFar: What are your goals in ultra racing going forward?

Roche: I think my plan is to do anywhere from one to two 50ks a year. For right now—I can see myself, down the road in 15 years, doing 50 milers and stuff like that. I have this inability to turn it off at the start line and so in a 50 miler I think I might do some pretty bad body damage and I want to avoid that. Being able to be out there running everyday is so important that I don’t want to risk doing any longer races.

Interview with Tim Tollefson

iRunFar: You ran your first ultra at the 2014 USATF 50k Trail National Championship and you won in a stellar time of 3:24. As an elite road marathoner, what influenced your decision to run an ultra?

Tim Tollefson: A combination of things really, I guess. I have wanted to get into trail running for a couple years, it just hasn’t really fit into my schedule. My heart was really with the marathon and I had so much tied in with achieving personal goals there that I was shutting out everything else. After my last two marathons—I felt they were kind of failures—I was feeling frustrated and was watching friends like Alex Varner and Chris Vargo having success and having a lot of fun on the trails. I was jealous and I thought, You know what, I want to get out there and give this a shot and see other trails around the country, and enjoy the process. So I want to try to reinvent myself a little bit the rest of this year and reevaluate in December.

iRunFar: How do you think your road-marathon background helps you in turning to the trails and ultra distances?

Tollefson: I think it definitely is a benefit. The greatest thing is coming from a history of consistency, just running mileage and building an aerobic base and learning how to suffer. There is a very challenging mental aspect to the marathon and you have to learn to deal with pain. I think it really goes across any part of our sport—5k, half marathon, 100 miler—you need consistency in training. I’ve been in the sport almost 15 years and have trained consistently throughout that and have a huge lifetime mileage base behind me. I think probably just having that history of thousands of miles behind me is a big factor. Having my speed from the marathon was a benefit versus most of the field but the top guys at Flagline were all fast marathoners—they had the same credentials if not better than me.

iRunFar: Do you think you have more advanced skill sets for the trails, relative to the other top guys at Flagline, outside of your speed that allowed you to prevail?

Tollefson: I do. From the nature of Mammoth Lakes—we sit at 8,000 feet and I can run from my house and get up to 11,000 in seven miles so I can do some pretty steep descents and ascents. I can get as technical as I want with the terrain, too—loose rocks, uneven terrain, or groomed singletrack trails. I studied the course at Flagline and really trained for the course and I think the specificity of my training was pretty dialed in. I knew altitude wouldn’t hurt me, since I live at a higher elevation than the Flagline course, and that may have assisted me a bit.

iRunFar: How did your training differ, if at all, for the Flagline 50k than from your road marathons in the past? Was there anything especially difficult about your first ultra?

Tollefson: I would say the three biggest changes I made to my training were running more mileage, incorporating more ascents and descents—overall elevation change—on long runs so that the time on my feet got longer, and then I did uphill tempos versus my straight flat tempos. In terms of my mileage, I think I had a three- or four-week period where I averaged 118 or 119 miles per week. That’s more than I had ever done for a marathon. I topped out at 124 for a seven-day period. I think having that consistency definitely just built the strength I already had aerobically. I did a couple 26-mile long runs that were around three hours, just trying to get used to that time on my feet and I would throw in technical descents at the end of runs to simulate being tired during a race. For Flagline, I cut my tempos in half and did around four or six miles but I made them uphill, which taught me to suffer uphill—something you don’t do in the marathon.

Later on in the race, one of the big challenges was the fueling aspect. I think I only took three gels and drank 22 ounces of fluid during the race. I thought I could get away with it since I was running just an hour longer than a marathon. But definitely during the final four miles of Flagline I was bonking hard. The more interviews I read with ultrarunners, it’s all about fueling. Fuel early and fuel often, and you can’t disregard that. That’s something I learned from this race—I really need to dial that in a little bit better in my training and racing.

iRunFar: You posted, on Flotrack in 2012, a blog called “CrossFit vs Ultrarunning. Which is more nauseating?” and received some negative feedback. What is the story behind that post, which you deleted not long after you posted it?

Tollefson: Yeah [laughs], that was back when I was a bit more of an asshole and thought I was funny. At the time I was working at a running store and had just finished graduate school. I was working retail with some guys who were in the ultra community. We got talking about all sorts of stereotypical things you see in runners and at races. It went from this private conversation that we were all laughing about—we were making fun of marathoners, too. I had never written a blog before so I thought I would give it a shot. But what we thought was hilarious in this private conversation—well, before I knew it, it had 14,000 or 15,000 hits. Some people thought it was hilarious, even ultrarunners, but then it struck a nerve with a lot of people.

I thought our sport might need someone to poke fun at things—kind of like Jim Rome in Rome Is Burning. You get a lot of the press that is scared to write truly objective things about runners because it’s a small community, and if you write something negative about [a big name], you’ll get shut off and won’t get an interview next time. In a sense, it kind of sucks, you know, if we runners can’t take criticism. It goes into what the rest of society thinks of us, like we are these weak athletes. I don’t think a little objectivity or humor is a bad thing or the worst thing in the world. That blog, at the time, was just something we were laughing about and it wasn’t malicious in intent. I was thinking about running ultras even at that time.

iRunFar: What are your goals in racing ultras going forward?

Tollefson: I guess it’s up in the air. I have been approached by a few people, and encouraged by others, to jump into The North Face Endurance Challenge 50-Mile Championship [in December]. I’m really not sure if I’m ready or want to do a 50-mile race yet, though. I’m not completely ruling it out. I would like to do something in November or December on the trails. It’s a matter of seeing what is available. Right now nothing is planned for the next two months. But I would like to continue to build with a trail focus.

Interview with Beverley Anderson-Abbs

iRunFar: You have proven to be a very dynamic runner, constantly racing sub-marathon distances along with 100 milers, including several attempts at the rugged Barkley Marathons. What got you competing in these events?

Beverley Anderson-Abbs: The big thing, my husband, Alan, and I got into adventure racing, and we started running ultras to train for the adventure races because in an adventure race you’re out there for two or three days and many hours of it could be on foot so we figured we better be able to run for some of that. So we started doing the ultras and then shifted over [to the ultras] once adventure racing became, just, shockingly expensive. Now, of course, we’re seeing the same thing happen in ultrarunning! Hopefully though we won’t see any runs hitting the $18,000 mark.

iRunFar: And your husband, is he still competing in ultras?

Beverley Anderson-Abbs: Yes, he is. Fairly often we race together. These last couple years we have separated a little bit because I have been doing more of the flatter, faster runs and he is trying to stay focused on mountains. So we’re doing things a little differently. We enjoy doing a lot of different things. A big part of doing the ultras was going to see different places. Doing that we ended up in Costa Rica, Hawaii a few times—it’s a cool way to go and see new places and take a vacation.

iRunFar: You won numerous 50k and 50-mile races in impressive times, perhaps most notably the 2014 Jed Smith 50 Mile in 6:14:46, where you set the overall Canadian women’s national record. Where you going after the record, were you aware of it?

Anderson-Abbs: Well the previous record was mine so I was aware of it. [laughs] No, I really didn’t have it on my radar at the time. I was looking for a good, solid 50-mile time so that I could continue to run on the Canadian 50-mile and 100k teams. So, when I went out for it, I was thinking if I could hit about a 6:30 I would be happy. But things sort of clicked and I felt really good and I ended up a little faster than I expected I would be.

iRunFar: What components of your training help to maintain or enhance your speed?

Anderson-Abbs: Well, when I look at times like what Emily [Harrison] runs, I look at my times and think, Wow, that’s kind of slow! [laughs] For 50 miles, I guess my pace per mile is pretty fast, but it’s more about holding a pace than doing it fast. I think a lot of people out there can run a seven-something pace per mile for some amount of time but it’s a matter of holding that pace steady for six hours. And then you look at some of these guys who are running 13 hours for 100 miles and that just isn’t even human as far as I’m concerned. [laughs]

But I do try to make sure I’m including some speedwork in my training and racing and that is while you’ll see so many different distances in my races. I like to get short, fast races in to make sure I’m keeping that speed in my legs. Generally, I try to do a good solid track workout once a week and then get something in—when I’m not in the middle of racing—on the weekends with some sort of tempo or fast race. I try to add in as much little bits of speed as I can.

I do different workouts depending on where I am on a schedule. One of my favorites is a 1600-meter, 800-meter alternating workouts. I do the 1600 at 6:30 to 6:40 per mile pace and then the 800 at 6:15 per mile pace. Then, the last couple weeks, I’ve been doing three or four 1600’s, three or four 1200’s, three or four 400’s. And I get a little bit faster with each of the shorter distances. I get bored with the same repeat so I mix things up a little bit and give my legs a little bit different work.

iRunFar: At the age of 49, you ran a personal-best time at the 50-mile distance. So you seem to continue to get faster! What might you attribute to this fact—experience, years of training, smart racing?

Anderson-Abbs: Picking the right course. [laughs] I guess it’s just staying consistent and keeping the training up and not letting things get in the way [of training]. A little bit of stubbornness involved, consistency is a big thing. And being able to pace smartly—I used to go out super fast and then die at the end. At Jed Smith, I started with the pace that I wanted rather than starting at a six-minute per mile pace. When I crossed the finish line [at Jed Smith], my first thought was, Wow, I wish that had been longer than a 50 mile because I could have gone further. So, I’ve probably become smarter and a lot more consistent with pacing and learned not to be too concerned with people who take off super fast. I tend to let them go and nine times out of 10 if I’m consistent I’ll eventually pass them.

iRunFar: How does your training change for a 100-mile race as compared to a 50k or 50-mile race? What sort of specific speedwork do you run?

Anderson-Abbs: For longer ultras, the big thing is just trying to add mileage and get out into the mountains more often. If I’m focusing on short things or flatter races, I’ll run close to home where we really don’t have hills. In getting ready for the Barkley Marathons, it’s about getting a lot of time and miles in the mountains. If I really focus on something like Barkley, I’ll drop out speedwork and focus more on the climbing. Even for 100-mile races, I’ll probably continue to do speedwork—for something like, say, the Vermont 100, I would definitely keep speedwork in. And I’ll typically lengthen the intervals of my speedwork for the longer ultras—like drop out the 400-meter repeats and go up to two-mile intervals.

iRunFar: What advice might you have for younger ultrarunners in terms of how to continue to improve and race for years?

Anderson-Abbs: I would say the biggest thing that I would advise is to enjoy themselves while they are doing it and don’t take it for granted because you can lose it in a heartbeat. I had a situation a few years ago where I had knee surgery and I was told that I would never run again. When you are facing that, it’s a tough place to be and you stop taking it for granted really fast. Be careful, and watch your body, and don’t push things that could potentially lead to an end of running. That’s a big thing—take care of yourself and don’t take it for granted.

iRunFar: What goals do you have going forward?

Anderson-Abbs: That’s a darn-good question, actually. I would like to continue to do all the various distances and terrain that I’m doing. But I’m starting to recognize that flat and fast is the way that my body wants to go now. I do struggle getting the hills in, especially since knee surgery—I can’t do what I used to do on hilly terrain. I’m trying to be realistic, but at the same time I’m optimistic that I can continue doing what I used to do. I don’t know. I don’t have goals but I do want to go back to the Barkley. I’m on the Canadian 50-mile team and the trail championship is in France next year, so I want to do that. But Barkley is killing me! Unfortunately, I didn’t have the body to manage it last year.

Call for Comments (from Meghan)

What lessons have you learned from these runners’ successful training that you can apply to your own?

What speedwork do you incorporate into your training and how do you adapt it to the changing characteristics (distance, elevation change, terrain, and more) of your changing goal races?

What are your thoughts on maintaining or minimizing loss of speed as we age? For those of us who have been at this a while, how do you keep you speed up year after year?

There are 2 comments

Course profile (including techy terrain, as well as % grade of hills/mountains) is a variable that a lot of "speedy flat folk" will take some getting used to (and vice-versa). This is most apparent in Euro style SkyRunning races IMHO. I think it comes down to musculature and running economy on variable terrain.

That being said, the benefits of even flat speed work is huge benefit for all MUT runners. The intense cardiovascular training of hitting Vo2max (or just above 90-95% max HR even) for intervals/fartleks as well as Lactate Threshold training gives you power on all uphills. Then the biomechanics/running form improvements like a higher cadence stride rate and landing under the center of gravity (usually improved when going higher velocities on uniform surfaces) will pay dividends in running economy at all sub maximal speeds (i.e. during ultra race pace on trails and variable terrain). Finally, the high amount of muscle tension generated from speedwork just flat-out makes your legs strong!

The running economy and musculature comment, I see that all the time. I am always amazed at how good faster runners with little to no trail background are for several miles into technical trail races. I've always described their struggle towards the end of longer races as a lack of trail specific endurance, but we are basically talking about the same thing. I think the key musculature adaptation is quad conditioning for downhils for the most, and the trail economy should come with more trail miles.